The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A principle of piezoelectric is to utilize a piezoelectric effect and an inverse piezoelectric effect. The piezoelectric effect refers to generation of the voltage when applying a force to both ends of the piezoelectric. Products to which the piezoelectric effect is applied include a shock sensor, a knock sensor and the like. The inverse piezoelectric effect refers to a phenomenon in which displacement occurs when a voltage is applied to both ends of the piezoelectric. Products using this phenomenon include an injector, an actuator and the like. As an example, in the case of the piezoelectric actuator, the displacement occurs when a piezoelectric top plate is contracted by the reverse piezoelectric effect.
Related prior art discloses a piezoelectric circuit. According to the prior art, the piezoelectric circuit includes a sub-piezoelectric circuit, and an external inductor connected in parallel to the sub-piezoelectric circuit. The external inductor discharges the sub-piezoelectric circuit, when the polarity of the piezoelectric voltage which is both end voltages of the piezoelectric circuit is inverted. Here, the sub-piezoelectric circuit includes a series resonant circuit which has a first capacitor, a first inductor, and a resistance connected in series to one another, and a second capacitor connected in parallel to the series resonant circuit.
The piezoelectric element can be used as a valve which regulates the inflow and outflow of air by utilizing the piezoelectric effect of the piezoelectric element. That is, when the displacement occurs by contraction or expansion of the piezoelectric element, holes into which air flows can be generated or removed by utilizing the displacement.
However, when the current remains in the piezoelectric element, it is not possible to accurately achieve the functions of the air valve, and leakage of air may occur.